World No. 7 star Juan Martin del Potro withdrew from next week's Madrid Open because of a viral infection.
"He has a virus and will not be fit to play," a statement on the tournament's website said. "We wish him a fast recovery."
The former U.S. Open champion from Argentina was a semifinalist in Madrid last year.
Madrid is a clay-court ATP Masters 1000 event and will feature the "Big Four" -- world No. 1 Novak Djokovic, three-time overall and reigning champion Roger Federer, Andy Murray and Rafael Nadal.